(1) Field of the Invention:
The present invention relates to ceramic articles having a shape memory effect, and a processing method and a joining method using such a shape memory ceramic article.
(2) Description of the Prior Art:
Although ceramics such as alumina, silicon nitride or the like have excellent properties in heat resistance, corrosion resistance, wear resistance, and mechanical strength, they cannot be worked through a cheap and easy plastic processing which is ordinarily carried out in the case of the metals, because the ceramics indicate no plastic deformation at room temperature or a temperature therearound. Therefore, the ceramics are processed by cutting, grinding, or polishing, and it is very difficult to precisely process them or process them into a complicated profile. Accordingly, there have been demanded ceramic articles which can be plastically processed at room temperature or a temperature therearound.
Incidentally, there are materials such as Ni-Ti alloy which have a peculiar physical property called "shape memory". The shape memory is a phenomenon which is attributable to a martensite transformation, that is, the transformation due to the shear deformation of the crystal lattice, and means that shape-restoring phenomenon occurs in a one way direction or reversibly between the shape on a higher temperature side and the shape on a lower temperature side across a transformation temperature range. Besides the Ni-Ti alloy, there are Cu-Cd alloy, Cu-Zn alloy, Cu-A-Ni alloy, Cu-Sn alloy and so on as the materials having the shape memory effect, but they are all metallic. The metals are not suitable for use under a high temperature oxidizing atmosphere and a corrosive atmosphere. Thus, there have been strongly desired ceramic materials which have excellent properties in heat resistance, corrosion resistance, wear resistance, and mechanical strength as well as shape memory effect.